Fuel injection systems for internal combustion engines

ABSTRACT

A fuel injection system for an internal combustion engine, in which, for the purpose of modifying the fuel/air ratio only under certain engine conditions, the return branch of the fuel circulation system includes a resiliently-biased valve member which functions to maintain the return branch fuel pressure at a value dependent on the resilient bias, and means for varying the resilient bias under the said engine conditions. In an embodiment, the bias on the valve member is increased when intake manifold vacuum drops below a predetermined value, enabling fuel enrichment to be achieved when the engine is developing full power.

Umted States 1191 [111 3,916,856

Jackson Nov. 4, 1975 [54] FUEL INJECTION SYSTEMS FOR 2,706,976 4/1955 Gianini 123/139 AW INTERNAL COMBUSTION ENGINES 2,727,504 12/ 1955 Peras 123/ 140 MP 3,712,275 1/1973 .lacksonm. 123/119 R Inventor: Hamld Ernest Jackson, Plymouth, 3,721,390 3/1973 Jackson 239/585 England a [73] Assignee: Petrol Injection Limited, Plymouth, Primary Examinerwendell Bums E l d Assistant Examiner -David D. Reynolds Filed Dec 26 1973 Attorney, Agent, or FirmBrisebois & Kruger 211 Appl. No.: 428,411

[57] ABSTRACT [30] Forelgn Apphcatmn Pnomy' Data A fuel injection system for an internal combustion en- Jan. 4, 1973 United Kingdom 569/73 gine, in which, for the purpose of modifying the fuel- /air ratio only under certain engine conditions, the rel l 139 123/1l9 turn branch of the fuel circulation system includes a 123/140 MP resiliently-biased valve member which 'functions to [51] Int. Cl. FOZM 51/00 maintain the return branch fuel pressure at a value de- [58] Field 0 Stiarc 140 139 pendent on the resilient bias, and means for varying 139 123/1 19 32 EA the resilient bias under the said engine conditions. In

an embodiment, the bias on the valve member is in- [56] References Cited creased when intake manifold vacuum drops below a UNITED STATES PATENTS predetermined value, enabling fuel enrichment to be achieved when the engine is developing full power. 2,456,605 12/1948 Wirth et a1. 123/139 AW 2,655,907 10/1953 Downing 123/140 MP 2,681,647 6/1954 Wille 123/139 AW 4 Claims, 1 Drawing Figure US. Patent Nov. 4, 1975 a XX;

ll. l m 3v A E 8v 8w m Q9 ma. NO. Qv h m? Q; q 9v H g F m R m 8w XX i FUEL INJECTI N SYSTEMS FOR INTERNAL COMBUSTION ENGINES This invention relates to fuel injection systems for internal combustion engines. 1 w

It is desirable to provide, in a fuel injection system, an arrangement for adjusting the ratio in which fuel and air are supplied to the engine so that, for example, a degree of fuel enrichment can be achieved under full throttle conditions. Such an arrangement may be manually controlled or it may come into operation automatically in response, for example, to throttle opening.

It is an object of the present invention to provide an arrangement which enables the fuel/air ratio to be modified automatically in response to a predetermined change in an engine operating parameter.

The invention provides a fuel injection system for an internal combustion engine, including a fuel circulation conduit system having supply and return branches, at least one injector device connected to receive fuel from the supply branch, and a fuel pressurizing'device operable to supply fuel under pressure to the supply branch, the return branch including a valve closure member resiliently biased towards a closed position and movable against the resilient bias by fuel pressure in the return branch to permit fuel flow through the return line to an extent sufficient to maintain the return branch fuel pressure upstream of the valve closure member at a predetermined valve dependent on the said resilient bias, and means operable to vary the resilient bias in response to a variation inan engine operatingparameter over part only of the range of that parameter.

The invention enables the amount of fuel discharged by the system to be modified under certain engine operating conditions and, more especially, enables the amount of fuel discharged to be increased when the engine is developing full power. To this end, the said means is operable to increase the resilient bias on the valve closure member in response to adrop in engine intake manifold vacuum to below a predetermined value. In an embodiment of the invention, the said resilient bias is substantially constant when the said means is unoperated, and the said means is operable to vary the resilient bias continously with variations in the engine operating parameter over the said part of the range of that parameter.

The valve closure member may be a resilient diaphragm resiliently biased by a spring.

The means operable to vary the said resilient bias may comprise a second resilient diaphragm which, when operated, is coupled to the valve closure member to vary the said resilient bias. The second resilient diaphragm may be biased towards the operative position by a spring. In an embodiment of the invention, the second resilient diaphragm is exposed on one side to engine intake manifold vacuum.

The injector device (s), may be operable to discharge fuel intermittently. The injector device(s), may, for example, be of the type described. in US. Pat. No. 3721390 of Mar. 20,1973 to Harold Ernest Jackson and may be operated by a control mechanism of the typedescribedin US. Pat. No. 3,712,275 of Jan. 23, 1973 to Harold Ernest Jackson. a

By way of example, .a fuel injection system constructed in accordance with the invention will be described with reference to the accompanying drawing which is a diagram of the system.

The system shown in the drawing is of the type described in the above mentioned U.S. Pat. No. 3,712,275 and reference may be made to that Patent for a detailed disclosure of various components of the system.

Basically, the fuel circulation path of the system includes a tank 1 from which fuel is drawn by a pump 2 (which may, for example, be an electrically-driven gear pump) and passed, at a substantially constant pressure to a supply conduit 3. A plurality of injector devices 5 (only one of which is shown in the drawing) are connected in the supply conduit 3 and, in operation, discharge fuel into the intake manifold system of the engine. More particularly, as shown in the drawing, each injector device 5 is positioned to discharge fuel into a respective cylinder intake branch 10a of the manifold system. Excess fuel, that is fuel which is not discharged by the injector devices is returned to the tank 1 through a return conduit 7 including a relief valve 6. The construction of the relief valve 6 differs from that described in the above-mentioned US. Pat. No. 3,712,275 and will, accordingly, be described in greater detail below.

The injector devices 5 are air-bled solenoid-operated devices of any suitable form but preferably of the type described in the above mentioned US. Pat. No. 3,721,390. In use, the injector devices 5 discharge fuel intermittently under the control of electrical pulses produced by a switching unit 8 to which each device is electrically-connected by leads 9. The switching unit 8 is connected to the battery and also, through leads l0] and 102 respectively, to the contact breaker and ignitionn switch of the conventional contact breaker circuit whereby the control pulses are generated at a rate dependent on engine speed. The length of the pulses, and hence the length of time for which the injector devices 5 discharge fuel, is adjusted with engine air intake. Details of the adjustment of the control pulse length are not necessary to an understanding of the present invention and may be obtained from the above-mentioned US. Pat. No. 3,712,275. Briefly, however, it may be mentioned that engine air intake is represented, for the purposes of adjusting the control pulse length, by the orientation of an air valve located in the engine air intake conduit 10 upstream of the customary throttle valve. The positions of the air and throttle valves are-indicated at 11 and 12 respectively. When the engine is in operation, the air valve 11 produces a control depression in the intake conduit 10 and the position of the air valve is adjusted, in response to a variation in the control depression from a predetermined valve, to return the depression to that predetermined valve. This adjustment of the air valve 11 is effected by a sensing valve 312 and servomechanism 307 and is accompanied by adjustment of a metering valve (not shown) controlling the rate at which air flows through a control line 13, which air flow in turn controls operation of a timing switch 14. The timing switch 14 is electrically-connected to the switching unit 8 by leads 14a and determines the length of the control pulses produced by that unit. The servomechanism 307 and the timing switch 14 both communicate, through conduits 103 and 104 respectively, with the intake conduit 10 immediately downstream of the customary air cleaner (not shown) but this has-no bearing on the present invention. If required, details of the construction and function of the components 307,312, 13 and 14 can be obtained from the above mentioned US. Pat.

Associated with the timing switch 14 arevalves 400, 401 which modify operation ofthetiming switch'in the manner described in US. Pat. No. 3,7l2,275, and thereby adjust the length of the control pulses, under certain engine conditions. The valves 400, 401 may, for example, be responsive to intake manifold temperature and cooling water temperature respectively. It should be noted,.however, that a separate valve for modifying operation of the timing switch 14 to achieve fuel enrichment when the engine is operating under full load is not included in the system since the function of such a valve is fulfilled by the relief valve 6.

The main portion of the relief valve 6 includes a valve closure member in the form of a resilient diaphragm 402 which separates two chambers 403 and 404 within the relief valve. The inlet 7A of the relief valve opens directlyinto the chamber 404 while the outlet of the relief valve is a port 78 surrounded by an upstanding valve seating 405 within the chamber 404. When the system is not operating, a spring 406 in the chamber 403 biases the diaphragm 402 against the valve seating 405 as shown in the drawing, in which position the disphragm cuts-off communication between the inlet 7A and outlet 78 of the relief valve.

A second resilient diaphragm 407 separates two further chambers 408 and 409 within the relief valve, of

which the chamber 408 communicates through a con.-

duit 410 with the engine air intake manifold downstream of the throttle valve 12 and is, accordingly, ex-

posed to intake manifold vacuum while the chamber 409 communicates through a conduit 411 with the intake conduit immediately downstream of the customary air cleaner (not shown). The diaphragm 407 carries a push-rod 412 which extends through the chamber 409 and into the chamber 403 of the main valve portion. When the system is not operating, a spring 413 in the chamber 408 biases the second diaphragm 407 into a position in which, as shown in the drawing, the push rod 412 engages the first diaphragm 402.

When the engine is operating under part-load conditions and intake manifold vacuum is comparatively high, a pressure differential exists across the second diaphragm 407, which opposes and is sufficient to overcome the action of the spring 413. The diaphragm 407 accordingly moves against the spring 413, taking the rod 412 out of engagement with the first diaphragm 402. The pump 2 delivers fuel to the supply conduit 3 and the fuel is discharged intermittently by the injector devices 5 as already described. The excess fuel passes along the return conduit 7 and into the chamber 404 of the relief valve 6, where the fuel pressure acts on the diaphragm 402 in opposition to the spring 406. When the fuel pressure in chamber 404 is sufficient to overcome the action of the spring 406 the diaphragm 402 moves away from the upstanding seating 405 to permit fuel to flow from the chamber 404 to the tank 1. If the pressure in chamber 404 increases further, the diaphragm 402 moves further away from the seating 405 to increase the return flow to the tank 1 whereas if the pressure in chamber 404 decreases the diaphragm 402 moves back towards the seating to decrease the return flow. The characteristics of the spring 406 are chosen so that the biasing force exerted by the spring is substantially constant over the range of positions of the diaphragm 402: as a result, a predeterminedsubstantially constant fuel pressure is maintained upstream of the 4 relief valve"6 provided that the pushrod 412 remains out of engagement with the diaphragm 402. The existence ofthis substantially constant pressure which, typically, is of the order of 20 p.s.i. ensure s, that the amount of. fuel discharged by the injector devices 5' during-each operating period depends solely on the lengthof'that period-1 M e The force'exerted' onthe second diaphragm 407 by the spring 413 is comparatively weak and is not sufficient to move the-push rod4l'2 into engagement with the first diaphragm 402 until the .throttle valve 12 is approaching the fully-open position and intake manifold vacuum has dropped to a comparatively low value (typically 5" Hg). When this occurs, the biasing force exerted by the spring 406 on the diaphragm 402 has added to it the resultant force on the diaphragm 407 (equal to the difference between the force exerted by the spring 413 andthe opposite, weaker, force due to manifold vacuum). As a result, the diaphragm 402 moves towards the seating 405 and the fuel pressure upstream'of the relief valve 6 rises from the substantially constant value referred to above by an amount corresponding to the aforesaid resultant force on the diaphragm 407. The increase in fuel pressure upstream of the relief valve 6 results in an increased amount of fuel being discharged by the injector devices 5 during each operating period or, in other words, in the required fuel enrichment under full throttle conditions. If the throttle valve 12 opens still further, inlet manifold vacuum falls further and the aforesaid resultant force on the diaphragm 407 increases further, bringing about a further increase in the amount of fuel discharged by the injector devices 5. If, on the other hand, the throttle valve 12 closes and intake manifold vacuum rises by an amount sufficient to take the push rod 412 out of engagement with the diaphragm 402 then fuel pressure upstream of the relief valve 6 returns to the predetermined substantially constant valve referred to above. A

it will be seen from the above description that the relief valve 6 acts directly on the fuel pressure to bring about the required fuel enrichment under full throttle conditions and, moreover, that the degree of fuel 'enrichment exhibits a desirable variation with intake manifold vacuum.

It will be appreciated that the use of a relief valve such as that shown at 6 in the drawing is not restricted to systems of the type described in US. Pat. No. 3,712,275 and is not even restricted to systems in which fuel is injected intermittently, but could be used with advantage in any system in which the quantity of fuel delivered to the engine is influenced by fuel pressure.

i claim:

1. A fuel injection system for an internal combustion engine, of the type including a fuel circulation conduit system having supply and'return branches, at least one injector device connected to receive fuel from the supply branch, a fuel pressurizing device operable to supply fuel under pressure toth'e supply branch, and valve means including a valve closure member which is connected in the return branchfand is resiliently biased towards a closed position the valve closure member being exposed to the fuel pressure upstream in the return branch and being movable against the said resilient bias by that'fuel pressure to an'e'xtent sufficient to maintain that fuel pressure at a predetermined value dependent on the said resilient bias, the system being 3. A system as claimed in claim 1, in which the valve closure member is a resilient diaphragm and is resiliently biased by a spring.

4. A system as claimed in claim 1, in which the valve closure member is a first resilient diaphragm, and said means comprises a second resilient diaphragm which is exposed to engine intake manifold vacuum and a pushrod which is mounted on the second resilient diaphragm and is co-operable with the first diaphragm to increase the said resilient bias. 

1. A fuel injection system for an internal combustion engine, of the type including a fuel circulation conduit system having supply and return branches, at least one injector device connected to receive fuel from the supply branch, a fuel pressurizing device operable to supply fuel under pressure to the supply branch, and valve means including a valve closure member which is connected in the return branch and is resiliently biased towards a closed position, the valve closure member being exposed to the fuel pressure upstream in the return branch and being movable against the said resilient bias by that fuel pressure to an extent sufficient to maintain that fuel pressure at a predetermined value dependent on the said resilient bias, the system being characterized by means exposed to engine intake manifold vacuum and movable, in response to a drop in manifold vacuum to below a predetermined value, into co-operation with the valve closure member to increase the said resilient bias and thereby increase the said fuel pressure upstream in the return branch.
 2. A system as claimed in claim 1, in which, when the said means is unoperated, the said resilient bias is substantially constant, the said means being co-operable with the valve closure member to increase the resilient bias continously with decreasing manifold vacuum.
 3. A system as claimed in claim 1, in which the valve closure member is a resilient diaphragm and is resiliently biased by a spring.
 4. A system as claimed in claim 1, in which the valve closure member is a first resilient diaphragm, and said means comprises a second resilient diaphragm which is exposed to engine intake manifold vacuum and a push-rod which is mounted on the second resilient diaphragm and is co-operable with the first diaphragm to increase the said resilient bias. 